'\" te
.\" Copyright (c) 2004, Sun Microsystems, Inc.,
.\" All Rights Reserved
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.TH USB_GET_STRING_DESCR 9F "Jan 5, 2004"
.SH NAME
usb_get_string_descr \- Get string descriptor from device
.SH SYNOPSIS
.nf
#include <sys/usb/usba.h>



\fBint\fR \fBusb_get_string_descr\fR(\fBdev_info_t *\fR\fIdip\fR,
     \fBuint16_t\fR \fIlangid\fR, \fBuint8_t\fR \fIindex\fR,
     \fBchar *\fR\fIbuf\fR, \fBsize_t\fR \fIbuflen\fR);
.fi

.SH INTERFACE LEVEL
illumos DDI specific (illumos DDI)
.SH PARAMETERS
.ne 2
.na
\fB\fIdip\fR\fR
.ad
.RS 10n
Pointer to the device's \fBdev_info\fR structure.
.RE

.sp
.ne 2
.na
\fB\fIlangid\fR\fR
.ad
.RS 10n
Language ID. Currently only USB_LANG_ID (English ascii) is valid.
.RE

.sp
.ne 2
.na
\fB\fIindex\fR\fR
.ad
.RS 10n
String index indicating descriptor to retrieve.
.RE

.sp
.ne 2
.na
\fB\fIbuf\fR\fR
.ad
.RS 10n
Address into which the string descriptor is placed.
.RE

.sp
.ne 2
.na
\fB\fIbuflen\fR\fR
.ad
.RS 10n
Size of buf in bytes.
.RE

.SH DESCRIPTION
The \fBusb_get_string_descr()\fR function retrieves a parsed string descriptor
from a device. \fIdip\fR specifies the device, while \fIindex\fR indicates
which descriptor to return.
.sp
.LP
String descriptors provide information about other descriptors, or information
that is encoded in other descriptors, in readable form. Many descriptor types
have one or more index fields which identify string descriptors.  (See
Sections \fI9.5\fR and \fI9.6\fR of the \fIUSB 2.0\fR specification.) For
example, a configuration descriptor's seventh byte contains the string
descriptor index describing a specific configuration.
.sp
.LP
Retrieved descriptors that do not fit into \fIbuflen\fR bytes are truncated.
All returned descriptors are null-terminated.
.SH RETURN VALUES
.ne 2
.na
\fBUSB_SUCCESS\fR
.ad
.RS 20n
String descriptor is returned in \fIbuf\fR.
.RE

.sp
.ne 2
.na
\fBUSB_INVALID_ARGS\fR
.ad
.RS 20n
\fIdip\fR or \fIbuf\fR are \fBNULL\fR, or \fIindex\fR or \fIbuflen\fR is
\fB0\fR.
.RE

.sp
.ne 2
.na
\fBUSB_FAILURE\fR
.ad
.RS 20n
Descriptor cannot be retrieved.
.RE

.SH CONTEXT
May be called from user or kernel context.
.SH EXAMPLES
.in +2
.nf
   /* Get the first string descriptor. */

    char buf[SIZE];

    if (usb_get_string_descr(
        dip, USB_LANG_ID, 0, buf, SIZE) == USB_SUCCESS) {
            cmn_err (CE_NOTE, "%s%d: %s",
                ddi_driver_name(dip), ddi_get_instance(dip), buf);
    }
.fi
.in -2

.SH ATTRIBUTES
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Architecture	PCI-based systems
_
Interface stability	Committed
.TE

.SH SEE ALSO
.BR attributes (7),
.BR usb_get_dev_data (9F),
.BR usb_string_descr (9S)
